Help, Universal Geneve model to identify

welcome to the forum, and congratulations on inheriting this watch from your grandfather.

Many UG time only watches do not have model names.

there are several odd things about the watch that make it difficult to identify, first off is the lack of any graphics on the dial. This seems unlikely to have come out of the factory this way, I would at least expect to see Universal Geneve on the dial, and probably swiss, and probably some hour/minute markings.

The way the caseback fits is strange, it appears to be much smaller diameter than the case? So that begs the question of if the caseback actually matches this case.

To proceed we need to see the markings on the inside caseback, and also the movement. It takes skill and proper tool to remove the caseback without causing any damage, so if you are not able to do this, it may be better to have a watchmaker do it for you, and then take pictures.

having those pictures will help a lot.